The design, construction and sale of athletic and other footwear that demonstrates improved comfort has attained very significant commercial proportions. Consequently, a great deal of effort has been expended to provide a more comfortable shoe particularly for runners and other athletes whose feet undergo extreme pressure during athletic activities. Thus, a very large number of insert and/or insole structures have been proposed to provide such added comfort and foot protection, particularly in the metatarsal-phalangeal and heel areas of the foot.
Among the proposed improvements is that disclosed in U.S. Pat. No. 5,542,196 to Kantro issued Aug. 6, 1996 that describes a innersole of two different materials one harder than the other, with the softer material located under the Ball and heel portion of the foot. While such a device provides one solution to the enhanced comfort problem, the device is multi-layered and fairly difficult to fabricate and therefore reasonably costly to produce. Additionally, it relies for its benefit on a difference in material properties, one harder than the other and therefore raises the potential that the softer material will deteriorate more quickly than the harder material.
It is well recognized by those familiar with the biomechanics of the human foot and ankle that in walking and running the foot passes through a cycle comprised of a number of phases often referred to as the gait cycle. One method of defining some of the portions of these phases as they relate specifically to the foot, is that the foot is “pronated” or more simply, relaxed, during that phase of the gait cycle when it about to and actually strikes the ground and assumes the foot-flat position, while it is defined as “supinated” or, more simply stiffened as it prepares to leave the ground for the toe-off position or the start of the next cycle. The reasons for this are fairly simple, intuitive and well understood. The foot is pronated as it strikes the ground so that it can adapt and adjust to the surface with which it is becoming engaged. The foot is supinated as it leaves the ground in the toe-off position so as to provide a levered platform to generate the drive or lift necessary to propel or launch the body forward toward the next step.
As evidenced by the large number of “new and improved” athletic shoes introduced each year that propose to improve running, jumping or other athletic performance, there have been numerous prior art methods proposed for enhancing athletic shoes to take advantage of the above-described foot positions and conditions to enhance athletic performance.
For example, U.S. Pat. No. 4,858,338 to Schmid, issued Aug. 22, 1989 describes a shoe sole insert made of an elastic material that purports to absorb and store energy as it is bent at the heel strike and midstance portions of the gait cycle and returns that energy to the wearer during and immediately following the toe off portion of the gait cycle.
U.S. Pat. No. 4,222,182 to Sears, issued Sep. 16, 1980 suggests the incorporation of a transverse spring steel member to accomplish absorption and regeneration of the energy acquired during the heel strike and midstance portions of the gait cycle.
U.S. Pat. No. 5,191,727 issued Mar. 9, 1993 to Barry et al. describes a propulsion plate for incorporation into footwear that includes a specially configured spring plate that extends beneath the medial but not the lateral portion of the heel, through the arch region, to and beneath the metatarsal head region and toe region to reduce the force spike at heel impact.
U.S. Pat. No. 5,052,130 to Barry et al., issued Oct. 1, 1991 describes an athletic shoe spring plate in combination with a viscoelastic midsole, the spring plate being fabricated of multiple layers of carbon fiber/polymer composite and having upturned heel and toe extremities.
While these and other similar proposed improvements have advanced the state of the art in foot comfort and performance for athletes, there remains a need for further improvements in foot comfort particularly for athletes as they continue to push their capabilities toward ever higher objectives, i.e. longer distances, higher jumps etc. and none of these prior art references alone or in combination suggests the unique structure described in this application that provides both comfort and the capture and return of energy generated naturally during the gait cycle.